Contact: David Sims
(603) 862-5369
Institute for the Study of Earth, Oceans, and Space

July 13, 2006

DURHAM, N.H. --
In a paper published in the July 2006 issue of Global Change Biology, University
of New Hampshire scientists George Hurtt, Steve Frolking, and coauthors show
that land-use activities over the last 300 years have substantially altered the
land surface in ways that are likely to have had profound effects on the Earth
system. Land-use changes have impacted some 42-68 percent of the global land
surface, according to the study, which used historical records, satellite data,
and computer modeling to reconstruct 216 different global land-use reconstructions
to derive the most comprehensive picture to-date.

“This is the first global land-use history description that’s
designed specifically to allow global carbon and climate models to assess the
impacts of land-use history both on the past and current sources and sinks
of carbon and climate,” says Hurtt, assistant professor of natural resources
at the UNH Institute for the Study of Earth, Oceans, and Space (EOS) and Department
of Natural Resources.

According to Hurtt, this global land-use data will allow the next generation
of coupled carbon-climate models, known as Earth-system models, to include
the most advanced representations of land-use practices yet, including the
first mapped estimates of the effects of shifting agriculture, logging, and
secondary recovering lands.

“Land-use activities are known to have added large amounts of carbon
dioxide to the atmosphere, altered surface reflectivity, and led to habitat
alteration and destruction,” says Hurtt. “A major challenge for
scientists now is to understand the combined effects of these activities on
the dynamics of the carbon-climate system. This study provides a key basis
for these assessments.”

Land-use history is critical to understanding the dynamics of the carbon-climate
system, not just for technical reasons but also for policy reasons. One of
the big policy debates is to what extent carbon sinks in ecosystems should
be able to offset carbon emissions. “It is important to know if a carbon
sink in an ecosystem today is simply the result of recovery from having been
cut down in the past, or a net new storage for carbon over the long term,” says
Hurtt.

Moreover, he notes, without this historical analysis of land-use activities,
even the most sophisticated models would be inaccurate. “Even if you
didn’t care about the past and wanted to focus on future global environmental
changes, you would still have to first ‘initialize’ your model
to the current state of the planet. Because the current state has been altered
by a history of land-use activities over most of the planet, knowledge of historical
activities increases the knowledge of the current conditions,” Hurtt
says of the work.

Late last year, Hurtt presented the land-use research, now published in Global
Change Biology, in a “platform” presentation at the Seventh International
Carbon Dioxide Conference held in Boulder, Colorado. Since that time, the presentation
has been downloaded more than 1,000 times by individuals interested in the
data.

UNH co-authors of the study include Berrien Moore and Matthew Fearon. The
study was also co-authored by Steve Pacala, Elena Shevliakova, and Sergey Malysev
of Princeton University, and Richard Houghton of the Woods Hole Research Center.